The present invention relates to a driven running gear having two individual running gears which are connected to each other and mutually steerable for low-platform rail vehicles, particularly for articulated vehicles which consist of at least two body parts articulated to each other, in which a steering linkage transmits the angle of bend of the body parts to the running gear in order to place the individual running gears in proper curve-radial position.
Convenient entrance conditions and a lover vehicle floor resulting therefrom which extends continuously over the entire length of the vehicle, are some of the essential demands made by the passengers with respect to the comfort of modern rail vehicles, particularly in municipal transit.
Furthermore, from the standpoint of the operator, stable straight-ahead travel and wear-free travel around curves are desired, this latter being closely related to the elimination of the screeching upon travel over curves which is found disturbing.
Further objects are light weight and reduction of the investment costs, for instance by reducing the number of axles for the same capacity of the vehicles.
In accordance with the prior art, it was attempted already at an early time to do away, in such light-weight construction articulated vehicles, with pivoted trucks which, due to their central loading, result in heavy truck frames.
Known older embodiments either employ for this purpose the so-called association steering axle or else provide a body part without axle which connects the two axle-supported body parts pivotally to each other.
In most cases, in these solutions, as a result of the play present in the axle bearing guides and the steering as well as the partial absence of damping, a rolling movement occurs in the form of a sinusoidal turning movement around the vertical axis, which results in unsteady travel of the vehicles.
Recently there has become known from European Application EP-(A2) 0 263 793 a running gear which, conceived of as a motorized two-axle truck, due to its low cranked-axle construction, accommodates use below a central body part or below the articulation, of low-platform rail vehicles having two or more articulated body parts.
For this purpose, in each case, two idle wheels are connected with an axle bridge which is arranged below their axle center points and is developed otherwise substantially in L-shape and is suspended in each case at the end of its length-wise girder-like arm in rotary symmetry to a diametrically opposite axle bridge which bears the second pair of idle wheels, articulately in vertical direction from an unsprung truck frame. Each of the axle bridges serves in its center to receive a central air spring, both of said springs having a multipartite rotary articulation on their top. The two outwardly directed end body parts as well as an undercarriage supporting frame which connects the two air springs and serves a central body part are supported therein, swingable around the vertical axis, the said supporting frame being pivoted in longitudinal direction via links to the axle bridges.
The drive equipment consists in each case of a motor which lies longitudinally between two pairs of idle wheels and is yieldably mounted on the unsprung truck frame together with secondary drive on both sides to the idle wheels, in which connection the transmission of force is effected by articulated shafts to bevel gearings with spur differential gearing which are arranged outside on the axle stubs. The brake equipment, consisting of block and magnetic rail brakes is also suspended from the unsprung truck frame.
The disadvantages reside essentially in the fact that the solution indicated is directed towards the construction of a truck in which neither curve-dependent control by at least one of the body parts is provided nor is radial setting of the wheels upon travel over a curve possible. Furthermore, the truck frame disclosed there, as well as all important attached parts such as motors and brakes, form a part of the unsprung mass of the truck.
Furthermore, from international application WO 85/05 602 a solution is known in which two idle-wheel individual running gears are detachably connected to each other by their integrated, rigid short-coupling parts and in this way form a four-wheel unmotorized running gear which by its low, cranked-axle construction permits the use below or adjacent to an articulation part of low-platform rail vehicles having at least two body parts.
For this purpose, in each case two idle wheels are connected with an axle bridge which is arranged below their axle center points, which bridge otherwise has a rigid coupling part and with it surrounds in longitudinally displaceable manner the rigid coupling part of an axle bridge which is diametrically opposite with mirror symmetry and bears the second pair of idle wheels. The axle bridges serve to receive in each case in their center a central air spring, the springs being turnable at their lower side on a ball turning ring and bearing on their top the corresponding end body parts via supporting arms by means of an annular support which has a combined axial/radial bearing into which the pivot pin of the articulation floor part engages. The annular supports of both end body parts are connected together via a rod coupling, the couplings being pivoted in longitudinal direction via links to the two telescopically insertable coupling parts which are arranged rigidly on the axle bridges. Furthermore, the end body parts are connected to the axle bridges by wobble supports.
The brake equipment consists of outside disc brakes the brake discs of which are arranged on the axle stubs, the brake actuation parts being suspended unsprung from a support of the axle bridge.
The disadvantages reside essentially in the fact that in the solution indicated neither curve-dependent control by at least one of the body parts is provided nor is radial adjustability of the wheels upon travel over a curve possible and, furthermore, the brake system indicated forms part of the unsprung mass.
Another disadvantage is that the height of the floor in the region of the (motorized) end trucks is raised by steps arranged transverse to the direction of travel.
Due to the disadvantages of the solutions indicated in the prior art, not only is the wheel/rail wear unfavorably influenced and the screeching around curves not eliminated but, furthermore, all accelerations of the wheel/rail contact are conducted directly and unsprung into load-bearing structural parts as well as their attachments, which, as is known, leads to undesirably high stresses there. Cracks or even the breaking of load-supporting parts are the result. By thread connections which become loose, individual parts which are of importance for operation are not infrequently lost upon travel. This endangers the safety and/or the proper operation in such a manner that the failure of the vehicle is finally brought about.